This invention relates to a new macrocyclic lactone immunosuppressant agent, a process for its production and its use in a human host for treatment of autoimmune diseases and/or prevention of organ transplant rejections. This application is a continuation of U.S. application 683,639 first filed on Apr. 11, 1991. Priority is hereby claimed to that application. In 1983, the United States Food and Drug Administration licensed cyclosporin, an anti-rejection drug that revolutionized the field of organ transplant-surgery. The drug acts by inhibiting the body's immune system from mobilizing its vast arsenal of natural protecting agents to reject the transplant's foreign protein. Although cyclosporin is effective in fighting transplantation rejection, it suffers drawbacks in causing kidney failure, liver damage and ulcers which in many cases can be very severe. Newer, safer drugs exhibiting less side effects are constantly being searched for. European Patent Publication No. 0184162 of Fujisawa Pharmaceutical Co., Ltd., describes the macrolids immunosuppressants FK-506 and FK-520. The latter is produced by S. hygroscopicus subsp. yakushimaensis No. 7238. Other immunosuppressants are described in European Patent Application Publication Nos. 0323042, 0323865, 0356399 of Fisons plc, Merck & Co. Inc., and Sandoz, respectively.